1. Field of the Invention
This invention relates to a process of marking hot steel ingots with dots or lines wherein a metallic material which does not exert an adverse effect on the desired properties of the steel is applied to the ingot by jet spraying.
2. Description of the Prior Art
In order to mark steel ingots, they may be provided with inscriptions immediately after they have been made, e.g., in a continuous casting plant. Considerable difficulties are involved in such marking operations because the steel ingots are to be marked when their surfaces are at a very high temperature of 800.degree. C., on an average. Whereas paints might be sprayed onto the surface of the ingot in the form of dots, such paints have a thermal stability only up to temperatures in the range of that surface temperature. Besides, the paint spray nozzles used to spray such paints tend to be clogged at the temperatures which are encountered so that the reliability in operation is highly reduced.
In order to avoid these disadvantages it has already been suggested to apply a metallic material rather than paint in the form of dots or lines to the hot surface of the block and to apply said metallic material by a flame spraying process in which the material is supplied in the form of a wire to a spray gun and is melted in said gun and is then atomized by means of compressed air and sprayed onto the steel ingots to be marked. Whereas the flame spraying of an aluminum wire has proved satisfactory as a process of marking steel surfaces which are cold or at moderately elevated temperatures, aluminum wire cannot be used to mark steel ingots having surface temperatures of or above about 600.degree. C. because aluminum that has been sprayed onto surfaces at a higher temperature will flow on the surface and will evaporate in part from the surface.
Whereas the temperature stability of the marking material might be increased by the use of high-melting metallic marking materials, such as nickel wire or titanium wire, such materials cannot be used in most cases because the colors of the oxides of said materials which are formed on the surface of the ingot hardly differ from the color of the iron oxide which constitutes the scale that is present on the surface of the ingot so that the inscriptions which are thus provided will hardly be legible. It has been attempted to avoid said disadvantages by the flame spraying of bronze or brass wire, which can be used to provide durable inscriptions on steel ingots even when the inscriptions are applied to surfaces at highly elevated temperatures. But such attempts have not been successful in practice because the copper that is contained in such alloys will considerably increase the susceptibility of the steel of red brittleness so that surface cracks may be formed on the steel ingots during their subsequent processing, e.g., by rolling or forging.